Surface cytometer for fluorescent detection and growth monitoring of bacteria over a large field-of-view

Monitoring the early onset of bacterial film formation is critical in many clinical, environmental, and food quality control applications. We built a small inexpensive optical surface cytometer, in contrast with bulk spectroscopic methods, around a light-emitting diode (LED) and a complementary metal-oxide-semiconductor (CMOS) image sensor. It is designed to offer a large field-of-view of 200 mm 2 and a large depth-of-field of 2-3 mm to overcome the limitations of routine methods like spectrophotometry and fluorescence microscopy. It provides a direct measurement without the need for complex image post-processing with a limit-of-detection around 10 4 cells/mm 2 , which is competitive with other similar yet more complex devices already available.